Development
Technical Details
Flight Testing
Cancellation
Insights
AEROPLANE JULY 2018 http://www.aeroplanemonthly.com 87DEVELOPMENT FAIREY ROTODYNE
conventional fi xed-wing airliner,
its ability to operate between
city centres would cut overall
journey times. Flights between
London and Paris, for example,
could take about an hour. The
company therefore believed
that the main civilian market for
the Rotodyne lay in Europe and
the populous areas of the
north-east USA. Ideal sector
length was believed to be up
to 200 miles (320km).
Bennett and chief mechanical
engineer Capt Archie Forsyth
had been thinking about an
airliner that could take off and
land vertically, transition to
forward fl ight and travel to its
destination twice as fast as a
conventional helicopter. In
1946 they started work on the
fi rst of two prototypes of a
small compound helicopter, the
Gyrodyne. It introduced many
new design features, and had
stub wings and an Alvis
Leonides radial engine driving
a conventional helicopter rotor
as well as a propeller to
provide forward thrust.
The fi rst Gyrodyne, G-AIKF,
made its maiden fl ight at
White Waltham, Berkshire, in
the hands of Sqn Ldr Basil
Arkell in December 1947. Six
months later Arkell fl ew it to a
new world speed record for
helicopters at more than
124mph (198km/h), but during
1949 the aircraft was lost in a
crash caused by rotor head
failure. Both of its occupants
were killed.
A second aircraft, G-AJJP,
was grounded following the
loss of the fi rst. It re-emerged
as the Jet Gyrodyne,
representing a major revision.
The Leonides engine now
powered a pair of Rolls-Royce
Merlin compressors to provide
air for the tip-jets. It also drove
two variable-pitch pusher
propellers mounted on the tips
of the stub wings. An initial
fl ight in this confi guration was
made in January 1954.
The tip-drive system had
been developed by the
Germans during the Second
World War. Several members of
the team behind it joined
Fairey after hostilities with a
free hand to continue their
research. A test centre was
established in a remote corner
of White Waltham airfi eld,transforming it into one of
Europe’s most advanced
aeronautical research facilities
at the time.
John Dennis was in
command when the Jet
Gyrodyne fl ew for the fi rst time
in January 1954. The main
objective of the subsequent
fl ight test programme was to
establish a viable and safe
method of operating the
Gyrodyne which could later be
adopted by the Rotodyne.
Several hundred successful
transitions were eventually
made, although it wasn’t until
the 1955 Farnborough show
that it could confi dently be
demonstrated in public.
Jet Gyrodyne take-offs
began by running up the rotor
on air only before the fuel was
introduced to ignite the
tip-jets. Once the blades were
turning the aircraft took off like
a helicopter with control, lift
and forward thrust provided by
the rotor, and yaw control
exercised via differential pitch
applied to the propellers.
When the aircraft was
established in forward fl ight the
tip-jets were shut down. Withthe rotor operating in
autorotation mode, the
engine’s main effort was
diverted from driving the
compressors to powering the
propellers. At that point the
rotor was providing most of the
lift with a small contribution
from the stub wings. Yaw
control now came from the
twin fi ns, supplemented by
differential propeller pitch.
During its initial studies
Fairey considered a variety of
powerplants for the Rotodyne.
At fi rst it envisaged that de
Havilland H7 engines mounted
in underwing nacelles would
generate air for the tip-jets.
Other units considered were
the Rolls-Royce Dart and
Armstrong Siddeley Mamba
turboprops in combinations of
two, three and four. The Napier
Eland was eventually felt the
most suitable.
Over the next few years the
project evolved from a
20-seater so that by the 1950s
it had become a 40-seater. At a
gross weight of 31,000lb
(14,000kg) this aircraft would
have cruised at 150mph
(240km/h). Range was given as185 miles (296km). It was noted
that a developed version, able
to carry 48-60 passengers over
250-350-mile (400-560km)
distances, could follow.
In April 1953 the Ministry of
Supply issued a contract to
Fairey for the construction of a
single prototype for research
purposes. It would be known
as the Rotodyne Y and later
received the military serial
XE521. At this stage Fairey’s
detailed operational analysis
suggested direct operating
costs of 3d (1.5p) per seat-mile
were realistic.
Dr George S. Hislop, who
had become Fairey’s chief
helicopter designer when
Bennett quit to join Hiller
Helicopters in California after
falling out with Fairey’s
management, told Flight in
1957 that the aircraft had been
designed to exploit the “heavy
potential” of short-haul city
pairs like London-Brussels and
London-Paris. Such operations
involved sector lengths of
230-260 miles (370-415km).
“The main emphasis”, Hislop
explained, “was directed to
achieving optimum economy
around this bracket”. But he
added that the aircraft’s
volumetric capacity and fuel
tankage could make it
attractive over much shorter
distances as well as longer
ones of up to 350 miles.
Wide rear loading doors,
combined with a large forward
door, made the Rotodyne a
highly fl exible proposition. It
could carry passengers, freight
and cars or mixtures of all
three. Hislop said that the
company’s main approach had
been concentrated on the civil
market although there hadPossibly the earliest artist’s impression of what was would become
known as the Rotodyne. This artwork is from a Fairey brochure
produced in December 1948. The basic elements of the design that
emerged are already visible. VIA RAF MUSEUMThe test rig featured a complete representation of the Rotodyne’s
rotor, powerplant and control systems. KEYSTONE PICTURES/ALAMY85-100_AM_Database_July18_cc C.indd 87 04/06/2018 16:57